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KVM: hlt emulation should take in-kernel APIC/PIT timers into account

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Timers that fire between guest hlt and vcpu_block's add_wait_queue() are
ignored, possibly resulting in hangs.

Also make sure that atomic_inc and waitqueue_active tests happen in the
specified order, otherwise the following race is open:

CPU0                                        CPU1
                                            if (waitqueue_active(wq))
add_wait_queue()
if (!atomic_read(pit_timer->pending))
    schedule()
                                            atomic_inc(pit_timer->pending)

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Marcelo Tosatti
2008-04-11 14:53:26 -03:00
committed by Avi Kivity
parent 3564990af1
commit 3d80840d96
8 changed files with 50 additions and 0 deletions
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15
arch/x86/kvm/irq.c
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@@ -25,6 +25,21 @@
#include "irq.h"
#include "i8254.h"
/*
* check if there are pending timer events
* to be processed.
*/
int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
{
int ret;
ret = pit_has_pending_timer(vcpu);
ret |= apic_has_pending_timer(vcpu);
return ret;
}
EXPORT_SYMBOL(kvm_cpu_has_pending_timer);
/*
* check if there is pending interrupt without
* intack.